Experiment Ivestigation Of Flame Acceleration And Numerical Simulation For CH₄-Air Premixed Gas In Tube

In view of the situation of explosive disaster of methane and other industrial flammable gases, premixed methane-air flame propagating in tube was investigated experimentally and numerically. The phenomena of flame acceleration propagation were described.Based on square transparent experimental tube(100mm×100mm) with 1440mm long, photoelectrical transducer, pressure transducer and high-speed video camera was used to set up optical and pressure signal testing system. The paper focuses on factors such as solid structure, blockage ratio, initial condition(methane concentration) and so on that have influence on flame propagation velocity and overpressure at measure points in tube. At the same time, whole process of flame propagation and interaction between flame and obstacle were screened by high-speed photography. And the numerical simulation has been carried on to the flame acceleration phenomenon. The results show below:1. Under condition of the same blockage ratio, plates and triple prisms have the most influence on flame propagation (flame velocity and overpressure) , while cylinders and Quadruple prisms have least influence on flame propagation. Cuboids are middle.2. The methane concentration has tremendous influence to the flame propagation velocity. When methane concentration is at about optimal concentration(about 9.62%(v/v)),flame velocity and overpressure reach maximum.3. When the flame crosses the obstacles, because of the friction of tube internal wall and the obstacle the flame will change the direction and eddies which being formed behind obstacle will occur.4. Obstacles prompt flame propagation.The acceleration mechanism of flame of methane-air premix is due to mutual feedback of turbulent combustion and gas flow which is induced by obstacles in pipe. Ultimate flame velocity and peak overpressure owe to obstacles.In order to study the relationship between the obstacle and the flame, the paper establishes mathematical model of flame acceleration with obstacles,the Phenomena that flame is accelerated by an obstacle and tube wall are investigated numerically. Simulation results reflect that obstacles are able to accelerate flame propagation to great extents. Simulation results show: Both obstacles and tube internal wall could accelerate the flame.The acceleration effect by an obstacle is more obviouse.Eddies which were formed behind obstacles aggravate turbulent flow. The forerunner pressure shock is created in the tube,which exceeding the flame surface.The research could use for reference to preventing and controlling explosion disaster of methane in coal mine and other industrial fields that present flammable gase. The deepens our understanding to combustion and explosion problem and also deepens our understanding to flame propagation in theory. At the same time, it can provide evidence for industrial safety design.